Exercises 1. Main idea

UNIT 1

Mainframes

[1] Large computer systems, or mainframes, as they are referred to in the field of computer science, are those computer systems found in computer installations processing immense amounts of data. These powerful computers make use of very high-speed main memories into which data and programs to be dealt with are transferred for rapid access. These powerful machines have a larger repertoire of more complex instructions which can be executed more quickly. Whereas smaller computers may take several steps to perform a particular operation, a larger machine may accomplish the same thing with one instruction.

[2] These computers can be of two types: digital or analog. The digital computer or general-purpose computer, as it is often known, makes up about 90 per cent of the large computers now in use. It gets its name because the data that are presented to it are made up of a code consisting of digits – single character numbers. The digital computer is like a gigantic cash register in that it can do calculations in steps, one after another at tremendous speed and with great accuracy. Digital computer programming is by far the most commonly used in electronic data processing for business or statistical purposes. The analog computer works something like a car speedometer, in that it continuously works out calculations. It is used essentially for problems involving measurements. It can simulate, or imitate different measurements by electronic means. Both of these computer types – the digital and the analog - are made up of electronic components that may require a large room to accommodate them. At present, the digital computer is capable of doing anything the analog once did. Moreover, it is easier to program and cheaper to operate. A new type of scientific computer system called the hybrid computer has now been produced that combines the two types into one.

[3] Really powerful computers continue to be bulky and require special provision for their housing, refrigeration systems, air filtration and power supplies. This is because much more space is taken up by the input/output devices - the magnetic tape and disk units and other peripheral equipment - than by the electronic components that do not make up the bulk of the machine in a powerful installation. The power consumption of these machines is also quite high, not to mention the price that runs into hundreds of thousands of dollars. The future will bring great developments in the mechanical devices associated with computer systems. For a long time these have been the weak link, from the point of view of both efficiency and reliability.

Exercises 1. Main idea

Which statement best expresses the main idea of the text? Why did you eliminate the other choices?

1. Hybrid computers are a combination of digital and analog computers.

2. Digital computers are used more than any other type of computer.

3. There are three types of mainframes.

4. Analog computers can do more varied work than digital or hybrid computers.

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